Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$173.91	6.356%	$184.9637	$184.96	$184.95	$185.00
Purchase #2	$195.37	4.848%	$204.8415	$204.84	$204.85	$204.80
Purchase #3	$250.89	3.181%	$258.8708	$258.87	$258.85	$258.90
Purchase #4	$158.51	13.300%	$179.5918	$179.59	$179.60	$179.60
Purchase #5	$186.32	7.573%	$200.43	$200.43	$200.45	$200.40
Purchase #6	$196.64	3.113%	$202.7614	$202.76	$202.75	$202.80
Purchase #7	$97.87	4.697%	$102.467	$102.47	$102.45	$102.50
7 purchase totals =	$1,259.51		$1,333.9262	$1,333.92	$1,333.90	$1,334.00